Most commercial processes for manufacturing anhydrous hydrogen fluoride (hereafter HF) involves the reaction of sulfuric acid on a metal fluoride, e.g., calcium fluoride or fluorspar. This reaction takes place in a rotary kiln, see for example U.S. Pat. No. 3,102,787. However, processes have been taught for this reaction involving a fluidized bed of particulate calcium fluoride, see U.S. Pat. Nos. 3,207,579 and 3,278,265, or by spraying preheated sulfuric acid on preheated particulate fluorspar, i.e., U.S. Pat. No. 3,469,939.
The reaction rate between calcium fluoride and sulfuric acid is fairly rapid; however, the processes in use to date have not been able to take advantage of this fact. Thus the art is still looking for methods for conducting this reaction which will reduce reactor hold-up time and can be conducted in simple equipment, thus requiring less investment and maintenance.